The present invention is related to distributed transmission systems for interrogating and monitoring the status of a number of remotely distributed data points, with. Such systems may exist in large buildings or on-board a ship or a plane, and the status information may consist of whether a hatch is open or closed, the temperature of a thermostat, etc. Typically in such systems, the individual data points are coupled to a processor in a point-to-point configuration on separate data buses or several data points may be multiplexed on one bus, but only one data point is interrogated at a time. An example of such a system is disclosed in U.S. Pat. No. 4,047,159 for remotely monitoring experimental instrumentation. Such systems, however, are relatively costly and require a great deal of hardware duplication for each channel and sub-channel and also require additional buffering and polling hardware to optimize system performance.
The present invention, however, is directed to a modular bus system for simultaneously interrogating a number of buses and the data points coupled thereto.
The present invention further discloses a bus system in which the transmitters are powered by the interrogation signals transmitted by the bus multiplexer.